<!doctype html> 
<html> 
<head> 
    <meta charset="utf-8">
    <meta content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0" name="viewport"> 
    <title></title>
    <style type="text/css">
*{margin: 0;padding: 0;list-style: none;}
html,body{
	height: 100%;
}
.div{
	width: calc(100% - 20px * 5);
	height:calc(5rem - 3px + 2.5%);
	background: black;
}



    </style> 


</head>
<body>

	<div class='div'></div>
</body>
</html>